If you want to push the envelop on this one – crumble a bit of your favourite blue cheese on top of the gratin!
Spicy Maple Walnuts
Beat egg and egg yolk in a large bowl with a whisk or fork. Add cream and milk. Beat to combine. Add the sweet potatoes and chopped herbs. Cover and refrigerate at least 1 hour or overnight.
Preheat oven to 350 degrees F. Line a baking sheet with parchment paper.
Add the walnuts to a medium sized bowl. Add cayenne, salt and maple syrup. Toss to coat. Spread the coated walnuts on the baking sheet. Bake on top rack until walnuts are slightly caramelized, about 10 minutes. Let cool slightly. Chop half of the walnuts into smaller pieces – the smaller pieces will be used between the layers of sweet potatoes. The bigger pieces will be used to top the gratin. Set aside.
Preheat oven to 350 degrees F.
Layer some of the sweet potatoes into a baking dish. Layer a sprinkle of the smaller pieces of walnuts. Continue to layer the gratin with sweet potatoes and nuts. Drizzle with any remaining cream mixture. Bake the gratin for 40 minutes and sprinkle with the remaining larger pieces of walnuts. Continue to bake until potatoes are tender and filling is golden and bubbly, another 10 to 15 minutes. Let stand 10 minutes before cutting. Slice and serve warm.